A leakage diagnosis apparatus for diagnosing presence/absence of refrigerant leakage in a refrigerant circuit performing a refrigeration cycle, wherein refrigerant leakage diagnosis using the amount of refrigerant exergy loss in a circuit component of the refrigerant circuit is realized. In a leakage diagnosis apparatus, an exergy calculation section calculates a leakage index value which changes in accordance with the amount of refrigerant leaking out of a refrigerant circuit based on the amount of refrigerant exergy loss in the circuit component. Then, a leakage determination section determines whether there is refrigerant leakage in the refrigerant circuit based on the leakage index value calculated by the exergy calculation section.